Temperature-responsive biodegradable injectable polymers with tissue adhesive properties

Immunomodulatory bioadhesive technologies

Bioadhesives have found significant use in medicine and engineering, particularly for wound care, tissue engineering, and surgical applications. Compared to traditional wound closure methods such as sutures and staples, bioadhesives offer advantages, including reduced tissue damage, enhanced healing, and ease of implementation. Recent progress highlights the synergy of bioadhesives and immunoengineering strategies, leading to immunomodulatory bioadhesives capable of modulating immune responses at local sites where bioadhesives are applied. They foster favorable therapeutic outcomes such as reduced inflammation in wounds and implants or enhanced local immune responses to improve cancer therapy efficacy. The dual functionalities of bioadhesion and immunomodulation benefit wound management, tissue regeneration, implantable medical devices, and post-surgical cancer management. This review delves into the interplay between bioadhesion and immunomodulation, highlighting the mechanobiological coupling involved. Key areas of focus include the modulation of immune responses through chemical and physical strategies, as well as the application of these bioadhesives in wound healing and cancer treatment. Discussed are remaining challenges such as achieving long-term stability and effectiveness, necessitating further research to fully harness the clinical potential of immunomodulatory bioadhesives.

An injectable controlled-release local anesthetic formulation of levobupivacaine based on a temperature-responsive polymer: Evaluation of analgesia, motor impairment, and histological toxicity in rats

PURPOSE

Postoperative pain management is extremely important for early recovery after surgery. However, effective and safe techniques for controlling postoperative pain are lacking. This study examined the effectiveness of controlled-release levobupivacaine for creating sciatic nerve blocks in a rat model of postoperative pain.

METHODS

A novel controlled-release injectable levobupivacaine gel was produced using a triblock copolymer of poly(ε-caprolactone-co-glycolide) and polyethylene glycol (tri-PCG). Male rats were used to create the incisional pain model. A single dose of controlled-release levobupivacaine (2.25%) gel, 0.25% levobupivacaine (clinical use), or tri-PCG was injected around the sciatic nerve of each rat immediately before paw incision. The pain thresholds were assessed preoperatively and up to 48 h postoperatively using von Frey filaments. Side effects were assessed using a motor impairment test, levobupivacaine blood level measurements, and pathological assessments.

RESULTS

The novel controlled-release levobupivacaine exhibited temperature-responsive sol-gel transition. In vitro, this formulation released 60% of its levobupivacaine content within 24 h. The withdrawal threshold was higher in the controlled-release levobupivacaine group than in the 0.25% levobupivacaine group at 6 and 12 h after paw incision. Motor impairment was not observed after controlled-release levobupivacaine injection, and the levobupivacaine blood level remained below the limit of detection throughout the assessment. On histopathology, weak signs of inflammation were detected in rat muscle and nerve tissues in the controlled-release levobupivacaine group.

CONCLUSION

A single injection of controlled-release levobupivacaine gel almost safely inhibited hyperalgesia for 12 h in a rat model. However, further research is needed on its effects on the surrounding tissue.

Vancomycin-Loaded in situ Gelled Hydrogel as an Antibacterial System for Enhancing Repair of Infected Bone Defects

Purpose

During treatment of infected bone defects, control of infection is necessary for effective bone repair, and hence controlled topical application of antibiotics is required in clinical practice. In this study, a biodegradable drug delivery system with in situ gelation at the site of infection was prepared by integrating vancomycin into a polyethylene glycol/oxidized dextran (PEG/ODEX) hydrogel matrix.

Methods

In this work, PEG/ODEX hydrogels were prepared by Schiff base reaction, and vancomycin was loaded into them to construct a drug delivery system with controllable release and degradability. We first examined the microstructure, degradation time and drug release of the hydrogels. Then we verified the biocompatibility and in vitro ability of the release system. Finally, we used a rat infected bone defect model for further experiments.

Results

The results showed that this antibacterial system could be completely biodegradable in vivo for 56 days, and its degradation products did not cause specific inflammatory response. The cumulative release of vancomycin from the antibacterial system was 58.3% ± 3.8% at 14 days and 78.4% ± 3.2% at 35 days. The concentration of vancomycin in the surrounding environment was about 1.2 mg/mL, which can effectively remove bacteria. Further studies in vivo showed that the antibacterial system cleared the infection and accelerated repair of infected bone defects in the femur of rats. There was no infection in rats after 8 weeks of treatment. The 3D image analysis of the experimental group showed that the bone volume fraction (BV/TV) was 1.39-fold higher (p < 0.001), the trabecular number (Tb.N) was 1.31-fold higher (p < 0.05), and the trabecular separation (Tb.Sp) was 0.58-fold higher than those of the control group (p < 0.01).

Conclusion

In summary, this study clearly demonstrates that a clinical strategy based on biological materials can provide an innovative and effective approach to treatment of infected bone defects.

Application of adhesives in the treatment of cartilage repair

From degeneration causing intervertebral disc issues to trauma‐induced meniscus tears, diverse factors can injure the different types of cartilage. This review highlights adhesives as a promising and rapidly implemented repair strategy. Compared to traditional techniques such as sutures and wires, adhesives offer several advantages. Importantly, they seamlessly connect with the injured tissue, deliver bioactive substances directly to the repair site, and potentially alleviate secondary problems like inflammation or degeneration. This review delves into the cutting‐edge advancements in adhesive technology, specifically focusing on their effectiveness in cartilage injury treatment and their underlying mechanisms. We begin by exploring the material characteristics of adhesives used in cartilage tissue, focusing on essential aspects like adhesion, biocompatibility, and degradability. Subsequently, we investigate the various types of adhesives currently employed in this context. Our discussion then moves to the unique role adhesives play in addressing different cartilage injuries. Finally, we acknowledge the challenges currently faced by this promising technology.

Advancements in hydrogel-based embolic agents: Categorized by therapeutic mechanisms

BACKGROUND

Transcatheter arterial embolization (TAE) is a crucial technique in interventional radiology. Hydrogel-based embolic agents show promise due to their phase transition and drug-loading capabilities. However, existing categorizations of these agents are confusing.

AIMS

This review tackles the challenge of categorizing hydrogel-based embolic agents based on their therapeutic mechanisms, including transportation, accumulation, interaction, and elimination. It also addresses current challenges and controversies in the field while highlighting future directions for hydrogel-based embolicagents.

MATERIALS AND METHODS

We conducted a systematic review of papers published in PUBMED from 2004 to 2024, focusing primarily on preclinical trials.

RESULTS

Various kinds of hydrogel embolic agents were introduced according to their therapeutic mechanisms.

DISCUSSION

Most hydrogel embolic agents were specifically designed for effective accumulation and interaction. Recent advancement highlight the potential of multifunctional hydrogel embolic agents.

CONCLUSION

This new categorizations provided valuable insights into hydrogel embolic agents, potentially guiding material scientists and interventional radiologists in the development of novel hydrogel embolic agents in transarterial embolization.

Development of immune cell delivery system using biodegradable injectable polymers for cancer immunotherapy

Immune cell delivery using injectable hydrogel attracts much attention for improving its therapeutic effect. Specifically, dendritic cells (DCs) are the trigger cells for immune responses, and DC vaccines are studied for improving cancer immunotherapy. Hydrogel-assisted cell delivery is expected to enhance the viability of the implanted cells. We recently reported temperature-responsive biodegradable injectable polymer (IP) formulation utilizing poly(ε-caprolactone-co-glycolide)-b-poly(ethylene glycol)(PEG)-b-poly(ε-caprolactone-co-glycolide) (tri-PCG). Tri-PCG-based IP was reported to exhibit immediate sol-to-gel transition in response to temperature increase, in vivo biodegradability, and excellent biocompatibility. In this study, tri-PCG-based IP was applied to DC delivery. IP encapsulated live DCs, and the DCs incorporated ovalbumin (OVA) as a model antigen and CpG-DNA (oligo DNA with adjuvant effect) in IP hydrogel. Results suggested that DCs encapsulated in IP hydrogel internalized OVA and CpG-DNA and DCs were maturated to present antigens to T cells. Moreover, subcutaneously injected tri-PCG-based IP prolonged the retention period of cell accumulation at injected sites. Tri-PCG IP hydrogel could release matured DCs as the degradation of the hydrogel progressed. Tri-PCG IP formulation improved treatment efficacy of OVA transfected mouse lymphoma (E.G7-OVA) tumor. Hence, tri-PCG IP is a promising platform for immune cell delivery.

AIE active luminous dye with a triphenylamine attached benzothiazole core as a portable polymer film for sensitively detecting CN- ions in food samples

Aggregation-induced emission (AIE) active 3-(3-(benzo[d]thiazol-2-yl)-2-hydroxyphenyl)-2-(4'-(diphenylamino)-[1,1'-biphenyl]-4-yl)acrylonitrile (BTPA) has been designed and synthesized herein, with the goal of detecting CN^- ions at a low-level in semi-aqueous medium. The deliberate addition of the electron-deficient alkene BTPA increased its sensitivity and selectivity to CN^- ions, with a better detection limit of 6.4 nM, unveiling the next-generation approach to creating sophisticated CN^- ions selective chemosensors. The ESI-MS and NMR spectra analyses provided strong support for the structures of the chemosensors, while the UV-Vis, photoluminescence, and ¹H-NMR titration experiments provided support for the sensing efficiencies. Subsequently, PVDF/BTPA electrospun nanofibers have been effectively produced as functional films. These nanofiber films exhibit outstanding mechanical strength, photo/thermal stability, and optical responsiveness to CN^- ions, making them a potential choice for on-field emerging contaminant detection.

A systematic study on the effects of the structure of block copolymers of PEG and poly(ε-caprolactone-co-glycolic acid) on their temperature-responsive sol-to-gel transition behavior

The effects of the molecular structure on the temperature-responsive sol-to-gel transition behavior and neat morphology of the block copolymers of poly(ethylene glycol) and poly(ε-caprolactone-co-glycolic acid) were systematically investigated.

An Injectable Peptide Hydrogel Constructed of Natural Antimicrobial Peptide J-1 and ADP Shows Anti-Infection, Hemostasis, and Antiadhesion Efficacy

Postoperative adhesion is a common complication of abdominal surgery, which always has many adverse effects in patients. At present, there is still a lack of effective treatment measures and materials to prevent adhesion in the clinics. Herein, we report the potential use of J-1-ADP hydrogel formed by natural antimicrobial peptide jelleine-1 (J-1) self-assembling in adenosine diphosphate (ADP) sodium solution to prevent postsurgery adhesion formation. J-1-ADP hydrogel was found to have good antimicrobial activity against the bacteria and fungi tested and can be used to prevent tissue infection, which was thought to be one of the incitements of adhesion. Due to ADP being a platelet-activating factor, J-1-ADP hydrogel showed significant hemostatic activity in vitro verified by whole blood coagulation, plasma coagulation, platelet activation, and platelet adhesion assays. Further, it showed potent hemostatic activity in a mouse liver hemorrhage model. Bleeding was believed to be a cause of the formation of postsurgery adhesion. J-1-ADP hydrogel had a significant antiadhesion effect in a rat side wall defect-cecum abrasion model. In addition, it had good biocompatibility and degradation properties. So the present study may provide an alternative strategy for designing antimicrobial peptide hydrogel material to prevent postoperative adhesion formation in the clinic.